Creating borders for flat models
You could try adding a raster image to your model as a texture:

Probably the easiest way to add a texture to your model is by dragging and dropping an image from a file manager onto your object in the 3D view:



Note that you'll also need to UV unwrap your object.

For simple 2D objects extruded along the Z (like the one in the above gif), you can probably get away with looking at your object from the top (Numpad 7) in edit mode (&#8633; Tab), and with everything selected (A), pressing U> Project from view.

For more detail, see


The wiki on UV unwrapping
The wiki on texturing
How to properly unwrap my mesh?